Field of the Invention
The inventions disclosed and taught herein relate generally to components of well bore fluids and muds, and more specifically are related to water-based drilling fluids and components therein which are suitable for use in oil/tar sand formations.
Description of the Related Art
When drilling or completing wells in earth formations, various fluids are typically used in the well for a variety of reasons. Common uses for well drilling and completing fluids include lubrication and cooling of drill bit cutting surfaces while drilling, particularly during drilling-in (drilling in a targeted petroliferous formation), transportation of “cuttings” to the surface, controlling formation fluid pressure to prevent blowouts, maintaining well stability, cleaning the well, transmitting hydraulic horsepower to the drill bit, and otherwise treating the well or formation.
In numerous rotary drilling operations, the drilling fluid takes the form of a “mud”—that is, a liquid having solids suspended in it. The solids function to impart particularly desirable rheological properties to the drilling fluid, while simultaneously increasing the density of the fluid in order to provide a suitable hydrostatic pressure at the bottom of the well.
Drilling systems are generally characterized as thixotropic fluid systems. That is, they exhibit low viscosity when sheared, such as when in circulation (as occurs during pumping or contact with the moving drilling bit). However, when the shearing action is halted, the fluid should be capable of suspending the solids it contains to prevent gravity separation. In addition, when the drilling fluid is under shear conditions and a free-flowing near-liquid, it must retain a sufficiently high enough viscosity to carry all unwanted particulate matter from the bottom of the well bore to the surface. The drilling fluid formulation should also allow the cuttings and other unwanted particulate material to be removed or otherwise settle out from the liquid fraction. Further, it is important that drilling fluids minimize the torque and drag that occurs in association with the drill string, particularly during the drilling operation itself.
There is an increasing need for drilling fluids having rheological properties to enable wells to be drilled while minimizing torque and drag, particularly in more challenging formations, such as oil/tar sand. Oil sand or tar sand, as they are generally referred to, more accurately termed bituminous sand, are a type of unconventional petroleum deposit. The sand contains naturally occurring mixtures of sand, clay, water, and a dense and extremely viscous form of petroleum technically referred to as bitumen (or colloquially “tar” due to its similar appearance, odor, and color). Oil/tar sand is found in large amounts in many countries throughout the world, but are found in extremely large quantities in both Canada and Venezuela, with other reserves being located in Kazakhstan and Russia. These types of formations often have unconsolidated sands, and exhibit highly varied porosity and permeability, which can cause high friction on a drill string during drilling operations, resulting in excessive torque and drag on the drill string and drill bit, stuck pipe incidents, and shaker screen blinding, to name only a few. Thus, historically, the majority of drilling operations in oil/tar sand and similarly difficult to drill formations have used oil- or hydrocarbon-based drilling muds, or have incorporated diesel or similar compounds as lubricants to counteract the problems in dealing with such formations. While the use of such lubricants in the drilling fluids improves lubrication to such an extent that it permits the drilling of wells in difficult formations as well as vertically-deviated wells (e.g., horizontal wells) where torque, drag and the potential for pipe sticking on the drill string are significant, the lubricating characteristics of such fluids must be balanced with environmental considerations in using such hydrocarbon-based fluids.
The inventions disclosed and taught herein are directed to improved drilling and completion fluids and systems for use in hydrocarbon recovery operations, wherein the systems exhibit improved rheological properties, particularly when the drilling operations are in oil/tar sand. In particular, it has been advantageously found that the dissipative surfactant described herein acts not only to lower the coefficient of friction, but also as a dispersant that generates a uniform drilling fluid mixture with improved flow properties due to its anti-agglomeration/dispersive characteristics on oil/tar sand.